Lipopolysaccharide (LPS) was partialy purified from E. coli O157:H7 local isolate by Sepharose – 4B gel filtration chromatography, after extraction by phenol-chloroform –petroleum ether mixture. The results show the presence of two peaks of proteins; while one peak of carbohydrates when tested at wave length 490nm. Nucleic acids were not found in the sample after partial purification. Electrophoresis pattern shows one large band with a molecular weight of 69000 daltons.